U.S. patent number 4,478,727 [Application Number 06/416,939] was granted by the patent office on 1984-10-23 for sodium styrene sulfonate-co-sodium-n-(4-sulfophenyl)-maleimide- an improved viscosity control additive.
This patent grant is currently assigned to Exxon Research & Engineering Co.. Invention is credited to Warren A. Thaler, S. Richard Turner, Thad O. Walker.
United States Patent |
4,478,727 |
Turner , et al. |
October 23, 1984 |
Sodium styrene sulfonate-co-sodium-n-(4-sulfophenyl)-maleimide- an
improved viscosity control additive
Abstract
A new copolymer of sodium styrene
sulfonate-co-sodium-N-(4-sulfophenyl)-maleimidehas been found to be
an improved viscosity control additive for water-based drilling
muds.
Inventors: |
Turner; S. Richard
(Bridgewater, NJ), Walker; Thad O. (Humble, TX), Thaler;
Warren A. (Aberdeen, NJ) |
Assignee: |
Exxon Research & Engineering
Co. (Florham Park, NJ)
|
Family
ID: |
23651934 |
Appl.
No.: |
06/416,939 |
Filed: |
September 13, 1982 |
Current U.S.
Class: |
507/108; 507/122;
525/327.5; 526/262 |
Current CPC
Class: |
C09K
8/24 (20130101) |
Current International
Class: |
C09K
8/02 (20060101); C09K 8/24 (20060101); C09K
007/02 () |
Field of
Search: |
;252/8.5A,8.5C |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Guynn; Herbert B.
Attorney, Agent or Firm: Nanfeldt; Richard E.
Claims
What is claimed is:
1. A water-based drilling mud which comprises:
(a) water;
(b) about 4 to about 30 lbs/bbl. of a clay;
(c) about 1 to about 30 lbs/bbl of a lignosulfonate;
(d) weighting material of sufficent quantity necessary to achieve
the desired density;
(e) about 0.25 to about 5 lbs/bbl. of a sodium styrene sulfonate
co-sodium-N-(4-sulfophenyl)-maleimide copolymer, said copolymer
being (1) prepared by copolymerization of sodium styrene sulfonate
and sodium-N-(4-sulfophenyl)-maleimide and having an Mn of about
10,000 to about 100,000, or (2) prepared by modification of a
preformed alternating styrene/maleic anhydride copolymer by
sequentially sulfonating the styrene pendant unit with SO.sub.3
followed by addition of sulfanilic acid to the enchained succinic
anhydride units, said preformed copolymer having a molecular weight
of from 1,000 to 500,000; and
(f) base of sufficient quantity to adjust the pH of the water-based
drilling mud to about 10 to about 10.5.
2. A water-based drilling mud according to claim 1 wherein said
sodium styrene sulfonate co-sodium-N-(4-sulfophenyl)-maleimide
copolymer is prepared by the copolymerization of sodium styrene
sulfonate and sodium-N-(4-sulfophenyl)-maleimide.
3. A water-based drilling mud according to claim 1 wherein said
clay is Bentonite.
4. A water-based drilling mud according to claim 1 wherein said
base is sodium hydroxide.
5. A water-based drilling mud according to claim 1 wherein said
sodium styrene sulfonate-co-sodium-N-(4-sulfophenyl)-maleimide
copolymer is prepared by modification of preformed styrene-maleic
anhydride copolymer.
Description
FIELD OF THE INVENTION
A new family of viscosification agents based on sodium styrene
sulfonate-co-sodium-N-(4-sulfophenyl)-maleimide is described as an
improved viscosity control additive for water-based drilling muds.
The resultant muds display good viscosity characteristics and good
stability when formulated from ionomers having an appropriate
sulfonate level, cation type and cosolvent content.
BACKGROUND OF THE INVENTION
In the field of drilling in the exploration for oil and gas, an
important component is that of the formulation of drilling muds.
Drilling muds are the fluids which are used to maintain pressure,
cool drill bits and lift cuttings from the holes and vary in
composition over a wide spectrum. Generally, drilling muds are
based on aqueous formulations or oil-based formulations.
A conventional water-based drilling mud formulation is comprised of
basically the following ingredients: water, a clay such as
bentonite, lignosulfonate, a weighing agent such as BaSO.sub.4
(Barite), and a caustic material such as sodium hydroxide and a
caustic material such as caustic barite, to adjust the pH of the
drilling mud to a pH of about 10 to about 10.5.
The continuing search for oil has placed greater demands on the
material packages that are utilized to conduct the drilling
processes. As drilling depth has increased, so has the bottomhole
temperature. In water-based drilling muds, elevated temperatures
result in the flocculation of the mud components and thus
problematic increases in mud viscosity. Over the years, a
progression of different additives has raised the maximum operable
bottomhole temperature. Recent disclosures have shown that
sulfonated low molecular weight styrene/maleic anhydride copolymer
is an effective water-based mud deflocculating additive. This
application describes the use of a new sodium styrene
sulfonate/sodium-N-(4-sulfophenyl)-maleimide alternating copolymer
as an improved additive for high temperature water-based mud
deflocculation.
This invention describes an approach to reducing the viscosity of
water-based drilling muds which is based on the addition of a water
soluble sulfonated copolymer to the mud. The resulting
polymer-modified drilling muds display viscosities which are in a
desirable range for drilling mud applications after aging at
temperatures as high as 400.degree. F. for 24 hours.
The types of sulfonated polymers that are envisioned in the present
invention are sodium styrene
sulfonate-co-sodium-N-(4-sulfophenyl)-maleimide copolymers.
SUMMARY OF THE INVENTION
The present invention relates to sodium styrene
sulfonate-co-sodium-N-(4-sulfophenyl)-maleimide copolymers which
function as viscosity reducing agents when added to water-based
drilling muds which are the fluids used to maintain pressure, cool
drill bits and lift cuttings from the holes in the drilling
operation for oil and gas wells. The sodium styrene
sulfonate-co-sodium-N-(4-sulfophenyl)-maleimide copolymers contain
pendant aryl metal sulfonate groups from each comonomer unit in the
copolymer structure.
GENERAL DESCRIPTION
The present invention describes a new viscosification agent for
water-based drilling muds which are used during operation of gas
and oil wells, wherein this viscosity reducing agent is sodium
styrene sulfonate-co-sodium-N-(4-sulfophenyl)-maleimide.
The water-based drilling muds of the instant invention minimally
comprise, but can also include other additives; fresh water or salt
water, a weighting material and a base to adjust the pH of the
water-based drilling mud to between about 10.0 to about 10.5. In
general, the specific gravity of about 7 pounds per gallon to about
20 pounds per gallon, more preferably about 10 to about 16, and
most preferably about 12 to about 16.
A typical water-based drilling mud, as envisioned by the instant
invention, comprises water or salt water; weighting material
necessary to give the desired mud density; about 0.25 to about 5
lb/bbl. of the sodium styrene
sulfonate-co-sodium-N-(4-sulfophenyl)-maleimide; and sufficient
concentration of the base to adjust the pH of the water-based
drilling mud to about 10.0 to about 10.5. Higher levels of the
sulfonated polymer can be employed but it is not normally
economically attractive. The drilling mud also contains a clay such
as Bentonite, at a concentration level of about 4 to about 30
lb/bbl., wherein the clay is added to the drilling mud to promote
circulation and improve hole stability and cleaning. A
lignosulfonate, which is a deflocculation agent, is added to the
drilling mud at a concentration level of about 1 to about 30
lb/bbl.
The solid copolymers of the instant invention comprise a copolymer
of N-(sodiumsulfophenyl)-maleimide and a sulfonate-containing
monomer characterized by the formula: ##STR1## wherein Y.sym. is a
cation selected from Groups IA, IIA, IB and IIB of the Periodic
Table or an amine of the formula: ##STR2## where R.sub.1, R.sub.2
and R.sub.3 can be aliphatic groups of C.sub.1 to C.sub.12 or
hydrogen and the copolymer being water soluble.
The monomers used in the free radical solution copolymerization
process are N-(4-sodiumsulfophenyl)-maleimide and a sulfonated
styrenic comonomer.
The comonomers are dissolved in a water phase in the presence of a
suitable free radical initiator, wherein the temperature is
sufficient to initiate polymerization. The resultant polymer can be
precipitated and filtered and dried under high vacuum.
The copolymers formed from the free radical solution
copolymerization of the instant invention can be generally
described as having an M.sub.n of about 5,000 to about 200,000,
more preferably about 10,000 to about 100,000.
The formed copolymers contain about 50 mol. % of
N-(4-sodiumsulfophenyl)-maleimide. The sulfonated styrenic
comonomer content is also about 50 mol. %.
The sulfonated styrenic monomers of the instant invention which are
water soluble can be generally described as monomers having
unsaturation and a metal or amine sulfonate group. The metal or
amine neutralized sulfonate monomer is characterized by the
formula: ##STR3## wherein Y.sym. is a cation selected from Groups
IA, IIA, IB and IIB of the Periodic Table or an amine of the
formula: ##STR4## where R.sub.1, R.sub.2 and R.sub.3 can be
aliphatic groups of C.sub.1 to C.sub.12 or hydrogen. Particularly
suitable metal cations are sodium, potassium and zinc, and an
especially preferred metal cation is sodium. A typical, but
non-limiting example of suitable sulfonate-containing monomers is:
##STR5## sodium styrene sulfonate.
An especially preferred sulfonate-containing monomer is a metal
sulfonate styrene. The molar ratio of sulfonate-containing monomer
to the N-(4-sodiumsulfophenyl)-maleimide is about 50 to about
50.
The N-(4-sodiumsulfophenyl)-maleimide monomer used in the free
radical solution copolymerization is prepared by a two-step
process. In the first step, maleic anhydride is reacted with
sulfanilic acid, sodium salt monohydrate in a methanol solution at
room temperature to form a half imide according to the reaction
scheme: ##STR6##
The formed precipitate of the half imide was recovered by
filtration and dried under high vacuum.
In the second step, the previously formed half imide is refluxed
with sodium acetate and acetic anhydride until a tannish color
developed. After cooling, the formed precipitate of the
N-(4-sodiumsulfophenyl)-maleimide is formed. The reaction scheme
is: ##STR7##
The copolymerization of the sulfonate-containing monomer with the
N-(4-sodiumsulfophenyl)-maleimide comprises the steps of dissolving
both the sulfonate-containing monomer and the
N-(4-phenylsulfophenyl)-maleimide in deoxygenated water at
50.degree. C. under N.sub.2 positive pressure and a water soluble
peroxy initiator is added to the solution. The reaction is allowed
to proceed for about 1 to about 48 hours, more preferably about 6
to about 24. Acetone is added to the reaction solution and the
resultant precipitate is filtered and dried under high vacuum.
The water soluble peroxy initiators are selected from the group
consisting of potassium persulfate and ammonium persulfate. The
concentration of initiator is about 5 to about 0.1 wt. % based on
total reaction solution, more preferably about 2 to about 0.5.
Water soluble redox initiators can also be employed in this free
radical solution copolymerization.
Chain transfer agents can be readily employed in the instant
polymerization process for controlling the molecular weight of the
resultant copolymer.
A second route to these copolymers involves the modification of
preformed alternating styrene/maleic anhydride copolymers. This is
accomplished sequentially by first sulfonating the styrenic pendant
unit with SO.sub.3, followed by addition of sulfanilic acid to the
enchained succinic anhydride units. The preformed polymer can range
in molecular weight from 1000 to 500,000.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
EXAMPLE 1
Preparation of Sodium Styrene
Sulfonate-Co-Sodium-N-(4-sulfo-phenyl)-Maleimide by
Copolymerization
To a stirred solution of 10.0 g. N-(4-sodium-sulfophenyl)-maleimide
(36.4 mmole) and 7.49 g. sodium-styrenesulfonate (36.4 mmole) in
100 ml. deoxygenated H.sub.2 O at 50.degree. C. under N.sub.2
positive pressure was added 0.01 g. potassiumperoxydisulfate (0.1
wt. %). The mixture was allowed to react for 24 hours then the
product was precipitated by addition of the solution to 2000 ml.
acetone. The pinkish, fibrous precipitate (VII) was filtered and
dried under high vacuum giving 14.28 g. (81.6% yield).
IR (film from H.sub.2 O): 3100 cm.sup.-1 (weak), 3060 cm.sup.-1,
(weak), 2190 cm.sup.-1 (weak), 1770 cm.sup.-1, 1700 cm.sup.-1, 1600
cm.sup.-1, 1200 cm.sup.-1, 1120 cm.sup.-1, 1035 cm.sup.-1, 830
cm.sup.-1, 710 cm.sup.-1.
Analysis Calcd. N, 2.92; S, 13.36; Found N, 3.05; S, 13.57.
EXAMPLE 2
Preparation of Sodium Styrene
Sulfonate-Co-sodium-N(-4-Sulfophenyl)-Maleimide by Polymer
Modification
Alternating 1:1 styrene maleic anhydride copolymer, 202 g. was
combined with 2000 ml. dichloroethane and 18.2 g.
triethylphosphate; 88 g. of sulfur trioxide was added slowly over
about 15 minutes. The mixture was stirred at ambient for several
hours and collected by filtration. The solid was washed with
several portions of ether and dried in vacuo. Titration indicated
that about two-thirds of the available styrene units were
sulfonated.
Sulfanilic acid, 17.3 g., was dissolved in 200 ml. of water
combined with 13.3 g. of 50% sodium hydroxide solution. The
sulfonated copolymer, 25.5 g., was added and stirred until
dissolved. The solution was placed in a pressure reactor which was
heated by a 190.degree. C. oil bath for 16 hours. The solution was
spray-dried using 125.degree. C. external temperature, and a
75.degree. C. outlet temperature. The product was a fine powder
weighing 35 g.
EXAMPLE 3
Test Mud Formulation
The following is a typical formulation for a fresh water
lignosulfonate mud. The density of this system can be adjusted as
desired by the addition of Barite (BaSO.sub.4).
______________________________________ Fresh water 350 cc Bentonite
22 lb/bbl. Lignosulfonate 5 lb/bbl. pH 10-10.5 w. NaOH
______________________________________
The Bentonite is added slowly to the fresh water so as to obtain
maximum yield or viscosity. This slurry is then aged overnight at
150.degree. F. To the cooled mud is added the lignosulfonate and
the pH is adjusted to 10 to 10.5 with caustic. Barite is added for
the desired weight (14.5 lb/gal). The mud is aged again overnight
at 150.degree. F. to insure chemical equilibrium. The pH of the
cooled mud is readjusted to 10 to 10.5 with caustic. To aliquots of
this base mud were added the dispersant stabilizers. These samples
were bombed at 400.degree. F. for 16 hours and then the rheological
properties were measured.
The results of testing (I) in comparison to the commercial Mil-Temp
deflocculation polymer are shown in Table I. Significant
improvements in the deflocculation efficacy of (I) versus Mil-Temp
were observed. At the one pound per barrel additive level, the 0
and 10 min. gel strengths are reduced by a factor of 5.5 to 7 and
the 600 and 300 rpm viscosities also significantly reduced.
TABLE I
__________________________________________________________________________
Comparison of Stabilizing Ability of (Copolymer (Example I) and
Mil-Temp Conc. Gels.sup.(e) Material lb/bbl. 600.sup.(a)
300.sup.(b) PV.sup.(c) YP.sup.(d) 0 10 pH Temperature
__________________________________________________________________________
Base >300 294 230 273 10.4 400.degree. F. + Copolymer 1/2
>300 195 5 7 10.4 400.degree. F. (Example I) + Copolymer 1 245
150 95 55 4 4 10.4 400.degree. F. (Example I) + Copolymer 2 252 167
85 82 4 5 10.4 400.degree. F. (Example I) + Mil-Temp 1 >300
>300 22 29 10.7 400.degree. F. + Mil-Temp 2 >300 280 10 12
10.8 400.degree. F.
__________________________________________________________________________
.sup.(a) = 600 rpm Fann Viscosity .sup.(b) = 300 rpm Fann Viscosity
.sup.(c) = plastic viscosity .sup.(d) = yield point .sup.(e) = 0
and 10 min. gel strengths
* * * * *